Fixing OrderBook#_subscribe (WIP).
Fixing OrderBook#_subscribe (WIP).

ripple/ripple-lib,ripple/ripple-lib,ripple/ripple-lib,wilsonianb/ripple-lib,wilsonianb/ripple-lib,darkdarkdragon/ripple-lib,wilsonianb/ripple-lib,ripple/ripple-lib,darkdarkdragon/ripple-lib,darkdarkdragon/ripple-lib